| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical recording medium capable of surely preventing the information of an optical recording medium from being copied. SOLUTION: In a compact disk 1 as an optical recording medium, an ordinary information signal is ciphered/recorded in an information recording area on an information recording surface. Moreover, a hologram 3 including enciphered key information for decoding an enciphered information signal is recorded in an area other than an information recording area, e.g. on a printing surface 2 on the opposite side of the information recording surface. Since the information signal is enciphered and recorded, even when all of the information signals are copied, the information signal can not be reproduced. Moreover since the enciphering key information for decoding the enciphered information signal is included in the hologram 3 being hardly duplicated, the hologram itself is not duplicated and consequently, the information copying of the optical recording medium is surely prevented. |
